If u put fan on your ESC but your whole heli/ESC is enclose in the fuselage and with no fresh going in, it is no use. The fan just keep on circulating the hot air. Maybe u can try putting a small fan just behind your turbine exhaust in order to push the hot air out.. and maybe another small fan near the swash plate to draw in fresh air.

Start by checking your electrical/gearing setup. Make sure your motor is being allowed to operate in the 80-90% efficiency. This can be controlled by getting the pinion on the drive motor down to a minimum number of teeth which in turn allows the motor to operate at higher rpm where it is much happier. Fans and such are typically bandaids for poor power train setups. Start here and also realize that scale flying does not require 2200+ rpm to fly correctly on a 500 size heli. Change the pinion to a lower tooth count and let us know if that helped.

Thanks for your help so, I explain how to fix this issue, thank you very much and that you have a good day

Hi guys , my fuselage has low temperature 5º celsius with two Pc fans at 12v in paralel connection , the air unside the fuse recircle , one fan expulse hot air and other refresh with out exterior cool air , Thanks